Syntheses of Macrocyclic Lactones

Lactones have also been synthesized from the rearrangement of cyclic compounds. Thus (51) undergoes base-catalysed isomerization and reduction to form the phenylsulphonyl lactone. The sulphone group is reductively cleaved with sodium amalgam and Na2HP04 to form the lactone.  

A novel series of lactones was synthesized by condensation of propiolac-tones to form the macrocyclic lactones (52), using the cyclic tin-oxygen compound (53) as a template.  

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An alternative procedure, starting with the enamine VIII/168, gave the twelve-membered oxolactone VIII/171 via VIII/169 and VIII/170 in a yield of 4% (from VIII/168, Scheme VIII/31), [97]. Syntheses of macrocyclic lactones with an annelated aromatic ring are described by various authors. Oxidations of compounds of type VIII/172 have been investigated in order to prepare aromatic oxolactones of type VIII/173, [99], Scheme VIII/3210). 

Intramolecular olefin metathesis has been used for the first time as the ring-closure step in syntheses of macrocyclic lactones (Scheme 13). A mixture of... 

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